1. Field of the Invention
The present invention relates to the field of welding, and more particularly to the cutting of various materials with welding equipment and attachments thereto.
2. Prior Art
Welders of various kinds are well known in the prior art. Of particular importance to the present invention are electric welders. In conventional electric welders, sometimes referred to as stick welders, welding progresses through the establishment of an electric arc between the end of a welding rod and the work piece or work pieces. Such welding rods are often provided with a suitable flux or flux generating material covering the metal rod, which material prevents the oxidation of the welding rod material and the adjoining areas to the work piece during the welding process. This type of welding equipment is well known and is relatively inexpensive. It also has the advantage that for small welding jobs, the operator can very easily change welding rods as to size so as to be able to weld thin material one minute and thick material the next, and to change rods as to material as appropriate for welding different materials. Such welders have the disadvantage, however, that for large welding jobs, the cost of the required welding rods is relatively high, and the welding process must be interrupted periodically for the replacement of the welding rod.
In recent years metal-inert gas (MIG) welders have gained in popularity and are now commercially available at reasonable prices. These welders are also electric arc welders, though include a hollow cable and special hand unit through which an inert-gas, such as carbon dioxide, is fed to protect the welding wire and weld area from oxidation. This allows the use of a bare wire as a welding rod, which is provided in coil form and fed through the hollow cable and special hand unit at an appropriate controllable rate to feed additional welding rod or wire as it is deposited in the welding process. Alternatively, in these welders a tungsten electrode may be used in place of the wire welding rod for the melting and/or fusing of the work piece or work pieces as desired.
Electric arc welders can be used for cutting also, typically by replacement of the metal rod by a graphite member and striking an arc with a work piece to gouge out the metal at the cut line. Because the cutting is by way of merely heating the metal to the melting temperature and allowing the metal to flow off the work piece, and because the resulting cut can only proceed at a limited rate, the resulting cut may be relatively jagged rather than clean, the process causes substantial heating in the adjacent work pieces, and frequently results in balls of melted and resolidified metal adhering to the region of the cut or adjacent regions of the work piece. In the case of thin metal, the heating of the adjacent work pieces may result in local yielding of the material from the stresses due to the thermal expansion thereof, resulting in a warping and untempering of the material when the work piece or pieces cool after cutting.
In the case of oxyacetylene torches, welding is accomplished by heating the metal to the melting point in a flame resulting from the burning of a mixture of acetylene and oxygen, the acetylene and oxygen being provided to the flame from separate containers therefor through separate orifices in the welding hand unit. For purposes of cutting, a cutting torch is used which establishes an initial flame much like an oxyacetylene torch for welding, though further includes a hand operated valve to direct jets of extra oxygen to the cutting region to assist in blowing the molten metal away from the cut. While such cuts are cleaner than result from the use of an electric welder, oxyacetylene cutting torches still provide a relatively rough cut, result in substantial heating of the work pieces, untempering of heat treated steel, and warping of thin material, and also may result in the solidification and/or fusing of molten metal in undesired locations.
In U.S. Pat. No. 866,498, a method of melting through masses of material is disclosed. In accordance with that patent, a hole may be made in steel plate such as armorplate by connecting, as asserted in that patent, "one pole of a circuit supplying electric current to the armor-plate, and the other pole is connected with an electrically conducting pipe through which oxygen is blown. Now if the armor-plate is contacted by the pipe and if oxygen is simultaneously blown through said pipe, only a flash of the short-circuit spark takes place, but the heat suffices for commencing the fusing and the oxygen perforates the plate in a fraction of a minute. It is here not a question of electric melting, or of a supply of oxygen to the electric arc; the action of the heating by the heat generated electrically and the melting through by means of the current of oxygen take place in point of time one after the other, as the current of oxygen indeed blows out the electric arc, or does not even allow it to form at all". (See also U.S. Pat. No. 999,099 for a related disclosure).
It would seem that the use of a pipe in the manner described could be satisfactory for effectively punching holes in plate as described, but that the same would not be very satisfactory for cutting plate and the like, as the unconfined oxygen emitted from the pipe would not give the desired oxygen jet characteristic. On the other hand, if a finer tubing was used, the desired oxygen jet characteristics might be achieved, though repeated arcing to initiate cutting would erode and perhaps deform the tubing exit, resulting in different and perhaps deteriorating cutting characteristics of the device over a period of time.
In U.S. Pat. No. 1,709,886, a cutting torch is disclosed wherein when the metal is heated to the proper temperature, a valve mechanism is operated to gradually cut off the supply of acetylene or fuel gas to the central or cutting orifice, after which the supply of oxygen to the cutting orifice is increased. The hand unit for this purpose is provided with four flow control valves rather than two as commonly found in normal oxyacetylene cutting torches. This valve mechanism is so constructed and arranged that a standard torch tip may be used with the cutting torch. However, while this feature would allow one having the special hand unit to have better access to tips of various sizes etc., the special hand unit required would make the cutting torch of Smith more expensive than a conventional oxyacetylene torch and thus subject to natural market resistance. In that regard, it is noted that while the cutting torch of Smith potentially could work very well, it is unclear what the commercial success of such torches might have been, though their apparent absence in the current market place at least indicates that for various reasons, they did not enjoy the long lasting success enjoyed by such other related technologies as electric arc welding in general, and conventional oxyacetylene cutting torches wherein a significant oxyacetylene flame is maintained even during cutting.
Other patents of interest include U.S. Pat. Nos. 894,195, 1,106,724, 1,247,791, 1,609,859, 1,494,003 and 2,524,223.